1. Field of the Invention
The present invention relates to a safety device for an automatic window opening and closing mechanism which is adapted to prevent a window in a vehicular door and roof from catching vehicle occupant's hand, neck and head when the window is closed by the automatic window opening and closing mechanism.
2. Description of the Prior Art
Conventionally, window panes of power windows and motor driven sunroofs are driven to automatically open and close by a motor, and such an accident sometimes happens that a vehicle occupant catches his hand and neck between a window pane and a window frame due to carelessness. To prevent such an accident, various safeguards have been devised for detecting a foreign object caught in a closing window pane to release the foreign object. An example of the safeguards includes a device disclosed in Japanese Patent Application Laid-Open No. 5-321530 (1993).
Referring to FIG. 4, the device is designed such that an automotive window pane 1 is opened and closed by an opening and closing mechanism 2 provided in a vehicular body under the window pane 1. Specifically, the opening and closing mechanism 2 includes a rail 3 extending in the vertical direction of the body, a slider 4 slidable vertically along the rail 3, and a wire 5 coupled to the slider 4 and mounted on pulleys 6 disposed at upper and lower ends of the rail 3 to be coupled to a power window driving portion 7 in such a manner that the slider 4 moves up and down by way of the wire 5 when the power window driving portion 7 is driven. The slider 4 is secured to a lower portion of the window pane 1, and a window space defined by a window frame 8 is opened and closed when the window pane 1 is moved upwardly and downwardly together with the slider 4.
The power window driving portion 7 includes a motor 9 serving as a driving power source. The motor 9 moves the wire 5 round to vertically move the window pane 1. For example, the window pane 1 moves upwardly to close the window when the motor 9 rotates in the forward direction, and moves downwardly to open the window when the motor 9 rotates in the reverse direction.
Referring to FIG. 5, a circular magnet 10 is fixed on a rotary shaft 9a of the motor 9. A pair of Hall elements 11a and 11b are disposed in different angular positions at a 90.degree. interval with respect to the rotary shaft 9a around the magnet 10 to form a pulse signal generating means 11. Since the Hall elements 11a, 11b produce a current upon detection of the magnetic poles of the magnet 10, the rotation of the magnet 10 resulting from the rotation of the motor 9 causes each of the Hall elements 11a, 11b to output a pulse signal having a frequency responsive to the speed of rotation.
FIG. 6 is a block diagram of the device. As illustrated in FIG. 6, the power window driving portion 7 is connected to a vehicle mounted power supply 21 and a function switch 22 such as a window opening switch and a window closing switch through a control unit 20. The control unit 20 includes a microcomputer 30. Output terminals of the Hall elements 11a, 11b serving as the pulse signal generating means 11 are connected to the microcomputer 30 through a sensor input circuit 23, and the microcomputer 30 is adapted to detect the speed and direction of rotation of the motor 9 in response to input pulse signals from the Hall elements 11a, 11b.
Opposite ends of the motor 9 serving as a driving power source are connected to the vehicle mounted power supply 21 through change-over contacts of two relays 24a, 24b and are grounded. Relay coils of the relays 24a, 24b are connected to the microcomputer 30 through a relay output circuit 26. Switching of the relays 24a, 24b under control of the microcomputer 30 allows the motor 9 to rotate in the forward and reverse directions.
The function switch 22 is connected to the microcomputer 30 through a switch input circuit 27 to select functions for switching between automatic and manual operations of the window and switching between opening and closing of the window. The vehicle mounted power supply 21 is connected to a power supply terminal of the microcomputer 30 through a constant voltage source 28 and is connected to the microcomputer 30 through an A/D converter 29 for analog-to-digital conversion of the output voltage from the vehicle mounted power supply 21.
FIG. 7 is a block diagram illustrating functions of the microcomputer 30. As shown in FIG. 7, the microcomputer 30 includes a system for detecting a safety control range in which the window pane 1 catching a foreign object should release the foreign object from a current position of the window pane 1, and a system for detecting the foreign object caught in the window pane 1.
The system for detecting the safety control range includes an opening and closing direction detecting means 31 for detecting the opening and closing directions of the window. The opening and closing direction detecting means 31, for example as shown in FIGS. 8A and 8B, binarizes the pulse signals outputted from the Hall elements 11a, 11b into two-bit signals to detect the direction of rotation of the motor 9 by detecting periodicity of variations in the two-bit signal values, thereby to detect the resultant opening and closing directions of the window. For example, when the order in which the two-bit signal values change is "2, 3, 1, 0" as shown in FIG. 8B, then it is judged that the motor 9 rotates in the forward direction. When the order in which the two-bit signal values change is "1, 3, 2, 0" as shown in FIG. 8A, then it is judged that the motor 9 rotates in the reverse direction.
The system for detecting the safety control range further includes a current position detecting means 32 having an up-down counter for detecting the current position of the window pane 1 indicative of the degree of opening and closing of the window pane 1. The current position detecting means 32 initially sets the count to zero when the window is fully closed. For example, the current position detecting means 32 counts the pulse signal in the negative direction when the motor 9 rotates in the forward direction and in the positive direction when the motor 9 rotates in the reverse direction to detect the current position of the window pane 1 in response to the count.
The system for detecting the safety control range further includes a safety control range judging means 33 for judging a predetermined range between a fully open position of the window and a nearly closed position thereof in response to the output from the current position detecting means 32 to perform control such that the window pane 1 catching the foreign object releases the foreign object only in the predetermined range.
In the nearly closed position of the window, the window pane 1 contacts the window frame 8, and the contact resistance causes a state similar to the state in which the foreign object is caught in the window pane 1. This position is used to prevent faulty detection at this time. In this device, the safety control range is defined as extending from the fully open position of the window to about 90% closed position of the window as shown in FIG. 4. A first output of the safety control range judging means 33 is applied to a first input of an AND gate 34, and a second output thereof is applied to an operation instructing means 35 serving as a catch release instructing means.
The system for detecting the foreign object caught in the window pane 1 includes an absolute velocity detecting means and a relative velocity detecting means.
The absolute velocity detecting means 36 detects a time interval between the turning on of a switch for opening and closing the window and the next rising edge of the pulse signal or between the adjacent rising edges of the pulse signal to judge whether or not the rotational speed of the motor 9, or the absolute velocity of the opening and closing window pane 1, is higher than a preset reference velocity. A first catch detecting means 37 detects the catch of the foreign object in the window pane 1 when the absolute velocity detected by the absolute velocity detecting means 36 is lower than the reference velocity, e.g. when the rotational speed of the motor 9 is less than 20 ms/rotation.
The relative velocity detecting means 38 detects time intervals between successive cycles of the pulse signal to derive angular velocity components of the motor 9 from the reciprocals of the time intervals. The relative velocity detecting means 38 then determines the amounts of change in opening and closing velocity which are detected as relative velocities. A second catch detecting means 39 detects the catch of the foreign object in the window pane 1 when the relative velocities are lower than a constant value, e.g. when the relative velocities are lowered by 10% or more from a steady value.
The outputs from the first and second catch detecting means 37, 39 are applied respectively to first and second inputs of an OR gate 40 which in turn provides an output to a second input of the AND gate 34. The output from the AND gate 34 is applied to a safety control operation instructing mean 41. Upon receipt of a catch detection signal from at least one of the first and second catch detecting means 37, 39, with the current position of the window pane 1 falling within the safety control range, the safety control operation instructing means 41 permits the operation instructing means 35 to operate to provide a catch release instruction to a motor driving circuit 42 to be described later. The motor driving circuit 42 in turn controls the motor 9 to open the window pane 1, for example, so that the window pane 1 moves 12 cm from the current position thereof in the opening direction.
It is needless to say that the operation instructing means 35 receives a signal from the function switch 22 to cause the motor 9 to rotate in the forward or reverse direction. The output from the operation instructing means 35 is applied to the motor 9 through the motor driving circuit 42 including the relay output circuit 26 and the relays 24a, 24b to control the rotation of the motor 9.
FIG. 9 illustrates characteristics (relation between an angular velocity .omega. and a load torque T) of general d.c. motors. A threshold level of the absolute velocity of the opening and closing window pane 1 determines a threshold level .omega.0 of the angular velocity of the motor 9 associated therewith, thereby determining a threshold level T0 of the load torque.
However, the conventional safety device for detecting the catch of the foreign object in the window pane 1 on the basis of the relative velocities does not ensure the detection of the catch since the relative velocities do not become lower than the constant value if the absolute velocity of the opening and closing window pane 1 changes gradually, e.g. when the window pane 1 catches a soft object.
In such a case, the device detects the catch on the basis of the absolute velocity, not on the basis of the relative velocities. However, when the window is opened and closed under the above described motor characteristics conditions, variations in friction between the window pane 1 and the window frame 8 or between the rail 3 and the slider 4 and in load such as an external force due to other factors might cause the angular velocity of the motor 9 to vary to .omega.1, .omega.2 depending upon the current position of the window pane 1 if the load torque T0 is constant as shown in FIG. 9. The variations in angular velocity vary the load torque of the motor 9 by T1, T2 from the threshold level T0 serving as a detection reference of the absolute velocity, resulting in unstable catch detection independently of the current position of the window pane 1.